I just installed the most recent Google platform-tools on my computer.
When I connect a phone (tried two different ones) it first works fine with adb - it is shown when calling 'adb devices' and opening a shell works fine.

After some seconds (30 or something), the device is shown twice as offline in 'adb devices'. When I wait some time, it keeps multiplying...

2 Answers
2

This is a frustrating issue, it happens mainly with phones that have a custom ROM installed on them. on top of restarting the ADB, you should restart the phone's debugging option, and try installing a different ROM.

I think the ROM is not the reason -- I tried two different roms on two different phones (MIUI and Cyanogenmod) - same issue. Restarting ADB does not fix it - device is shown offline and keeps multiplying...
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koch.trierFeb 9 '12 at 15:55

I had a similar issue - I had multiple devices showing under adb devices - all where offline except one (when my device was plugged in)

I just went to my adb and ran the kill-server command:

c:....\platform-tools>adb kill-server

This released all my "offline" devices and allowed me to connect my single device again.

While this will solve the problem temporarily I don't think it's the solution. It seems that there is either a problem with the phone or with the cable. In my case, I believe it to be the phone. I have noticed this happens when I move the phone with the cable plugged in. (i.e. it's a hardware issue)